Near infrared microscopy a simple but effective technique to analyze microdefects in GaAs

Sonnenberg, K.; Altmann, A.

Book/Report

FZJ-2018-06849

Near infrared microscopy a simple but effective technique to analyze microdefects in GaAs

Sonnenberg, K.FZJ* ; Altmann, A.FZJ*

1994
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich

Jülich : Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag, Berichte des Forschungszentrums Jülich 2939, 107 p. (1994)

Please use a persistent id in citations: http://hdl.handle.net/2128/20207

Report No.: Juel-2939

Abstract: The main structural microdefects in GaAs are point defects (native defects, dopants), dislocations, precipitates, and inhomogeneities of point defects. Microdefects are important because they directly affect the single crystal yield during the growth process and the properties of the crystal after growth. It has been shown [1] that the transition from single to polycrystalline growth is primarily caused by a local increase in the dislocation density near the crystal surface. When single GaAs crystals are used as substrate material for electronic devices microdefects significantly influence the device performance. Dislocations, for example, have a detrimental influence on the lifetime of minority carriers and the carriers mean free path; they degrade semiconductor lasers due to their role as nonradiative recombination centers [2]. It has also been shown that inhomogeneities in the substrate material are linked to fluctuation in the threshold voltage, V$_{th}$ of field effect transistors, thus impeding the exploitation of large scale integrated circuits (LSI). Understanding the mechanism which are causing the formation of microdefects will help to find ways to reduce their number or to minimize their detrimental influence. Several mechanisms for the nucleation of dislocations have been discussed in the literature. Because the entropy term of a dislocation is so much smaller than its energy, dislocations do not exist in thermodynamic equilibrium. The following heterogeneousnucleation mechanisms are possible: $\cdot$ Surface damage such as scratches have been identified. $\cdot$ Surface roughness which may form near the growth front due to loss of arsenic by evaporation have not been clearly identified but could be a major source for dislocations and could also playa role for initiating olycrystalline growth [3, 4]. $\cdot$ Chemical inhomogeneities resulting in the formation of misfit dislocation have been discussed as a possible reason for the formation of dislocation cells. Some evidence will be presented that this correlation is very unlikely. $\cdot$ Second phase particles can generate dislocation by their volume misfit or by a differences in thermal expansion between particle and matrix [2]. $\cdot$ Agglomeration of point defects resulting in loop formation has also been discussed. Although we know some possible nucleation mechanism for dislocation it is not clear which of them dominates during the growth of crystals. The major effort in the present work was directed towards studying of inhomogeneities in the surrounding of dislocations due to their interaction with doping and nativedefects. Dislocation can $\cdot$ act as nucleation sites for the formation of precipitates $\cdot$ interact with doping and native defects to form Cottrellatmospheres and associated denuded zones $\cdot$ react with native defects-As-interstitital or Ga-vacancies, respectively. As a result the dislocation perform a climbing step and Ga-vacancies or As-interstitials, respectively, are emitted. These reactions are driven by a substantial excess of arsenic [...]

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